The latencies are the delays in clock cycles caused by the time it takes for the RAM chips to perform specific functions. Although clock speeds are increasing, the RAM silicon speed isn't increasing much. Therefore it takes more clock cycles to perform the same tasks. A clock frequency of 1333MHz with a latency of 9 equates to a memory response time of 6.75ns. A speed of 1600MHz at a CL of 11 equates to a 6.78ns response. Compared to desktop DIMMS with their overclocking abilities, SODIMMS presently have limited speed/latency options. You can get high speed, low latency desktop DIMMS if you're willing to pay the extra price.